1. Field
Example embodiments relate to a semiconductor memory device, for example, to a phase changing material, a phase change random access memory (PRAM) including the same, and methods of manufacturing and operating the same.
2. Description of the Related Art
In a PRAM, a phase change layer where data is stored may change between crystalline and amorphous depending on temperature. When the phase change layer is crystalline, a PRAM has a lower resistance. When the phase change layer is amorphous, the PRAM has a higher resistance. A PRAM is a nonvolatile memory device that writes/reads bit data on/from the phase change layer using the resistance difference of the phase state.
Conventional PRAMs may require a high reset current Ireset to change the phase change layer into an amorphous state.
As a result of the development of semiconductor technology, it is not difficult to increase the integration level of a PRAM by reducing the size of transistors and storage nodes including the phase change layer.
However, when transistor size decreases, the maximum allowable current of the transistor also decreases. Therefore, it may be difficult to increase the integration level of the PRAM without the reduction of the reset current.
Because the conventional PRAM has a lower crystallization temperature, it may be more easily affected by its surrounding environment. This may degrade the reliability and/or retention properties of a conventional PRAM.